Left ventricular non-compaction (LVNC) is a rare heart condition where the walls of the left ventricle (the lower left chamber of the heart muscle) are non-compacted. The left ventricle is the heart's main pumping chamber and normally has smooth walls. In LVNC, the walls of the left ventricle have channels, called trabeculations, that give the ventricle a characteristic spongy structure. That is why this condition is also known as "spongy cardiomyopathy". This can affect how the heart works. Trabeculations can disrupt normal electrical signaling in the heart, leading to arrhythmia (heart rhythm disorders) that can sometimes be fatal. The non-compaction can affect the heart's capability to fully relax and contract, making it harder for the heart to efficiently pump blood.
How and why does LVNC happen?
Your heart starts to form early in life when a baby is still an embryo. It starts as a tubular structure of heart muscle cells. At this point, the heart doesn’t have arteries, so numerous channels, called trabeculations form to help the heart get enough oxygen and nutrients. In the next step of the development, heart muscle cells are brought closer together to form a thick, compact wall.
In people who have genetic LVNC, the compaction event is interrupted, leaving a large proportion of the muscle wall in the non-compacted form. A ventricle is considered non-compacted when the non-compacted layer is at least two times thicker than the compacted layer. Up to 40 percent of LVNC cases can be traced to a genetic cause. People who have this are born with it, but symptoms can occur at any age or might not occur at all.
LVNC can also be acquired, meaning that it develops later in life as a result of another condition or a different lifestyle (like in athletes). Sickle cell anemia, chronic kidney failure, pregnancy, and being an athlete have been associated with LVNC. Interestingly, acquired LVNC can potentially be reversible.
Better alone than in bad company
The diagnosis and classification of LVNC remain a somewhat controversial question in the medical community, with no official agreement. The World Health Organization (WHO), American Heart Association (AHA), and the European Society of Cardiology all have a different classification of this condition. LVNC has been recognized as a condition fairly recently and there is a lack of data, with most studies being based on a small number of case reports.
Cardiomyopathies are heart muscle diseases that affect how the heart works. LVNC by itself describes structural changes in the ventricle walls that don’t necessarily mean an impaired function. For example, LVNC has been observed in healthy young athletes with a normal size and function of the left ventricle. In one study, the condition of people with asymptomatic LVNC and no other changes in the heart muscle was followed for 10 years. They found that it wasn’t associated with a deterioration of the volume and the function of the left ventricle.
However, that is not usually the case. In many patients, LVNC is accompanied by other structural changes in the left ventricle that affect how the heart works. That’s why some people with dilated cardiomyopathy, hypertrophic or restrictive cardiomyopathy also have LVNC. When LVNC is associated with dilatation, hypertrophy or dysfunction of the ventricle, the genetic causes can overlap. LVNC is rarely an intrinsic part of cardiomyopathy, like in a very rare condition called infantile tafazzinopathy (cardiomyopathy caused by a mutation in the TAZ gene).
What are the symptoms of LVNC?
Symptoms that may occur in adults and older children include:
- Palpitations (a feeling that your heart is pounding in your chest).
- Arrhythmia (irregular heartbeat).
- Breathlessness with exertion or at rest (fluid builds within the lungs, making it harder to breathe).
- Fatigue and tiredness (due to lack of oxygen).
- Swelling of the legs and ankles.
Symptoms in newborns and babies are more likely to include:
- Excessive sweating.
- Poor growth.
- Difficulties with feeding.
How is LVNC diagnosed?
There are currently no official diagnostic criteria for LVNC. To get enough information for the diagnosis, your physician might require various tests and information. That includes:
- Medical history. Your doctor will ask you about all of the symptoms you might’ve been experiencing that can indicate the presence of LVNC or a condition that has been linked with LVNC.
- Family history. Between 17 and 50 percent of people who have been diagnosed have a family member who also suffers from LVNC. Because the condition can be inherited, family testing is always recommended.
- Physical exam.
- Echo (echocardiography). An echo is the most commonly used initial test for the diagnosis of LVNC. This test uses sound waves to produce images of your heart that allow your physician to see the structure of your heart, how it beats and pumps blood. Different types of echo can be used. Your doctor will look for trabeculations, how prominent they are, the thickness of the ventricular walls and the ratio between the compacted and non-compacted layer. If there are changes indicative of LVNC, an additional test may be recommended for the diagnosis to be confirmed.
- Cardiac magnetic resonance imaging (CMR). An accurate diagnosis for LVNC can be challenging and in the last few years, there has been a trend of overdiagnosing when just an echo was used. CMR provides higher resolution images and can give additional information that might be important for the treatment and the prognosis of the disease, like the degree of fibrosis. Fibrosis is scarring of the tissue and it’s considered to be a bad sign.
LVNC: Treatment and management
Treatment for LVNC can be very different for different people, depending on their symptoms and condition. Although there is no cure, symptoms can be managed and serious complications like sudden cardiac death can be avoided.
- Monitoring. People who have no symptoms often don't require any treatment, but the condition should be monitored to avoid complications.
- Medications. Medications are used to avoid complications that might occur or to treat the symptoms. The most common complications with LVNC are dangerous arrhythmias that can cause sudden cardiac death, the formation of clots that can lead to stroke and heart failure. You might be prescribed anticoagulants (blood thinners) to prevent clot formation. Medications for heart failure include diuretics (water tablets), ACE inhibitors (medications that reduce the workload on the heart) and medications to lower your blood pressure.
- Devices. If the medications are not enough to treat arrhythmias, certain devices like pacemakers or ICDs (implantable cardioverter defibrillator) might be recommended. A pacemaker restores a normal heart rhythm and ICD lowers the risk of death if the heart stops beating. Ventricular fibrillation and ventricular tachycardia are the most dangerous arrhythmias that can lead to sudden cardiac death.
- Heart surgery. Heart surgery is used as the last line of treatment for the most advanced cases.